Carb is Driving me Crazy!

[mtbman]

Ok, my bike wants to idle at 6000+ RPM.  So far I have replaced the plugs on the 4 vacuum ports that I know of, replaced the two little tiny o-rings at two of those vacuum ports, replaced the cracked intake manifolds and their o-rings, rebuilt floats with new needles, set float hight just below the gasket, and installed a stage three jet/needle kit from dynojet.  The throttle snaps shut, and the sliders slip down very quickly.  I can find no cracks in the diaphram on the sliders.  Anybody have any more ideas?  I am at a total loss as to what to try next. :dunno:   Thanks again for your help guys.
mike

[John Bates]

I'm not an engine expert, don't even know how the choke works, but I do know that when I forget to turn the choke off my engine idles really fast.  I'm sure you've checked the choke lever position, but how about the choke mechanism itself? :dunno:

[Kerry]

When you say "The throttle snaps shut" are you just saying that the return spring is in good shape?  Or are you saying that by examination you know that the butterflys are pulled back as far as they can possibly go?

I only have experience with pre-'01 (single-cable) throttle assemblies, so I'm not sure how this applies to the newer models.  But check to see if, when the throttle snaps back, the "stop" actually bottoms out on the upper end of the idle adjustment screw.  If it does, lower the idle screw until the stop doesn't touch it.

Is the idle still super high?  Let's assume that it is.  The next thing I would try is to loosen up the throttle cable a little bit.  It's easier to access and adjust it on the upper end near the handlebar.  But if there's no more adjustability there you'll have to get fancy with a pair of 10mm open-end wrenches (or something similar) at the carb end of the cable.  Fiddle with it for a while and you'll figure it out.  (This is one area that I don't have a good picture of....   )

If you have already tried these things I'll have to think some more....

[Dom]

Yeah...cover the basics you havn't mentioned...Idle adjust? How many turns out?  I'm not familiar with the DJ kit but you have to drill and tap all kinds of crap, eh?  If you don't figure out what is wrong I would bite the bullet and get some new diaphraghms and try Srinath's method: #150 mains, #40 pilots(no holes on sides, 37.5 w/ holes on sides) 1 #4 SS washer on needle, 3 turns out.  Cost me $20 and a trip to the Suzuki dealer and she runs like a champ.

I wrestled with a bad petcock for too long and it caused all kinds of wierd crap.  Didn't figure out what was wrong until I switched out all the lines for clear nylon tube.  I saw that there were bubbles forming behind the carb(starving) so I made a temp tank and routed a line direct to the carbs and everything ran great.  It turned out to be a bad petcock...which worked fine until I rejetted and started pulling a higher volume of fuel thru it...couldn't take the pressure, literally.

[The Buddha]

Set air screw to 3 or 3.5 or 4 or whatever ... just dont exceed ~5 turns out... if that dont work ... install 40 pilots ...
Now you said you put needles from DJ kit in ... why stage 3 ... you have K&N pod and pipe If not K&N pod try a stage 1 ... Dom's Idea 150/40 will be only for stock needle ... DJ needle ... no 150 for sure and I have no idea of the 40's ... the guy I rejetted that have the DJ's in them ... haven't responded back about how it is.
If its 6K all the time then try the idle screw ... 1100 when cold and 6K when hot = air mix screw etc...
Cool.
Srinath.

[mtbman]

When you say "The throttle snaps shut" are you just saying that the return spring is in good shape?  Or are you saying that by examination you know that the butterflys are pulled back as far as they can possibly go?

I only have experience with pre-'01 (single-cable) throttle assemblies, so I'm not sure how this applies to the newer models.  But check to see if, when the throttle snaps back, the "stop" actually bottoms out on the upper end of the idle adjustment screw.  If it does, lower the idle screw until the stop doesn't touch it.

Is the idle still super high?  Let's assume that it is.  The next thing I would try is to loosen up the throttle cable a little bit.  It's easier to access and adjust it on the upper end near the handlebar.  But if there's no more adjustability there you'll have to get fancy with a pair of 10mm open-end wrenches (or something similar) at the carb end of the cable.  Fiddle with it for a while and you'll figure it out.  (This is one area that I don't have a good picture of....   )

If you have already tried these things I'll have to think some more....

Thanks for the tips Kerry, the butterflys do snap shut vissually, I will recheck to make sure they are actually hitting the stops.  As for the slight slop in the throttle cable, I just did that the other day.  I wanted to make sure the cable wasn't holding any tension on the butterflys.  By the way, the carb is on a '92 so it is the old style.  If you come up with any more ideas I would love to hear them.  Thanks for your time.
mike

[mtbman]

Yeah...cover the basics you havn't mentioned...Idle adjust? How many turns out?  I'm not familiar with the DJ kit but you have to drill and tap all kinds of crap, eh?  If you don't figure out what is wrong I would bite the bullet and get some new diaphraghms and try Srinath's method: #150 mains, #40 pilots(no holes on sides, 37.5 w/ holes on sides) 1 #4 SS washer on needle, 3 turns out.  Cost me $20 and a trip to the Suzuki dealer and she runs like a champ.

I wrestled with a bad petcock for too long and it caused all kinds of wierd crap.  Didn't figure out what was wrong until I switched out all the lines for clear nylon tube.  I saw that there were bubbles forming behind the carb(starving) so I made a temp tank and routed a line direct to the carbs and everything ran great.  It turned out to be a bad petcock...which worked fine until I rejetted and started pulling a higher volume of fuel thru it...couldn't take the pressure, literally.

I am certainly thinking about going the Srinath's method, I wish I had found this board before I bought the jet kit.  As for the petcock, I don't have one on my bike, it used to have all the cali smog stuff on it and when that was lost I ditched everything.  I almost wonder if it try to give the carbs too much fuel?  Thanks for your time on this,
mike

[mtbman]

Set air screw to 3 or 3.5 or 4 or whatever ... just dont exceed ~5 turns out... if that dont work ... install 40 pilots ...
Now you said you put needles from DJ kit in ... why stage 3 ... you have K&N pod and pipe If not K&N pod try a stage 1 ... Dom's Idea 150/40 will be only for stock needle ... DJ needle ... no 150 for sure and I have no idea of the 40's ... the guy I rejetted that have the DJ's in them ... haven't responded back about how it is.
If its 6K all the time then try the idle screw ... 1100 when cold and 6K when hot = air mix screw etc...
Cool.
Srinath.

I have the carb master himself helping, yeah!  I do have the pod and pipe on the bike, that is why I went for the stage 3, though I am thinking about getting rid of it (I kept my stock needles after reading your thread).  The air screws are way in at 1.25 turns right now, I had them at 3 and the issue seemed even worse.   Basicly what has been happening is every time I try to fix the carbs they seem to idle pretty well, I tune them up a bit with the mixtrue screws and then go for a ride.  By the time I get back from the ride the bike idles at 6K.  From that point on the bike wants to idle at 6K no matter how cold it is :dunno: .  Thanks for helping on this,
mike

I am beginning to suspect an evil gnome living in the air filter.

[The Buddha]

Oh well 1.25 on air screws ... I am surprised it even runs ... set it to 3 ... and if you still have the barely hold 1000 when cold and 6K when hot ... starte opening it ... till you get to 5 or so ... if makes no diff, deep six the pilots and put in 40 non bleeds. That was what sorted my idle eventually. If you want to get the whole DK kit and caboodle out well then 150 and stock needles and washer.
Oh BTW you should have the floats set to the gasket level, to the top of float bowl and no more.... you said below the gasket ... that might be worth checking and sorting out.
Rip in diaphragm ... = different symptoms... you may not make over 6K under even mild load ... like in first you'd make 8-9K, 2nd gear and 7-8K, 3rd 6-7K, 4th 5-6K, 5th 5K and under... 6th 5K and under ... was what mine did with a tiny virtually impossible to see rip ... so hard to see in fact I opened the thing 20+ times, and finally swapped carbs and fixed the issue ... and over a year later someone told me what their carbs did with a rip in diaphragm and I open mine ... which were in a box at this point only to see that tiny rip ... and go d-oh...
Cool.
Srinath.

[JCH]

I'm actually having somewhat of a similar problem.   I rode today for about 3.5 hrs and my idle was fine, right around 1500-2500.  Once I got into stop and go traffic my idle jumped all the way up to 4500 and stayed like that until I shut ti down for about an hour.  I assume this has something to do with the bike not getting enough air, but being that the previous owner did some aftermarket rejetting + airbox I'm a little more concerned.

Post up once you know what the problem is, I may have something similar going on.

Good luck with fixing it!

[The Buddha]

Yea idle racing when hot = lean ... but only when traffic for a while = super hot and idle races only then  = slightly lean ... you should be able to open the air screws 1/4 turn and be perfect...
Cool.
Srinath.

[JCH]

Oh Cool!    Thanks a bunch Srinath!